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1// SPDX-License-Identifier: GPL-2.02 3#define pr_fmt(fmt) "ACPI: " fmt4 5#include <linux/pci.h>6#include <linux/acpi.h>7#include <acpi/reboot.h>8#include <linux/delay.h>9 10#ifdef CONFIG_PCI11static void acpi_pci_reboot(struct acpi_generic_address *rr, u8 reset_value)12{13 unsigned int devfn;14 struct pci_bus *bus0;15 16 /* The reset register can only live on bus 0. */17 bus0 = pci_find_bus(0, 0);18 if (!bus0)19 return;20 /* Form PCI device/function pair. */21 devfn = PCI_DEVFN((rr->address >> 32) & 0xffff,22 (rr->address >> 16) & 0xffff);23 pr_debug("Resetting with ACPI PCI RESET_REG.\n");24 /* Write the value that resets us. */25 pci_bus_write_config_byte(bus0, devfn,26 (rr->address & 0xffff), reset_value);27}28#else29static inline void acpi_pci_reboot(struct acpi_generic_address *rr,30 u8 reset_value)31{32 pr_warn_once("PCI configuration space access is not supported\n");33}34#endif35 36void acpi_reboot(void)37{38 struct acpi_generic_address *rr;39 u8 reset_value;40 41 if (acpi_disabled)42 return;43 44 rr = &acpi_gbl_FADT.reset_register;45 46 /* ACPI reset register was only introduced with v2 of the FADT */47 48 if (acpi_gbl_FADT.header.revision < 2)49 return;50 51 /* Is the reset register supported? The spec says we should be52 * checking the bit width and bit offset, but Windows ignores53 * these fields */54 if (!(acpi_gbl_FADT.flags & ACPI_FADT_RESET_REGISTER))55 return;56 57 reset_value = acpi_gbl_FADT.reset_value;58 59 /* The reset register can only exist in I/O, Memory or PCI config space60 * on a device on bus 0. */61 switch (rr->space_id) {62 case ACPI_ADR_SPACE_PCI_CONFIG:63 acpi_pci_reboot(rr, reset_value);64 break;65 66 case ACPI_ADR_SPACE_SYSTEM_MEMORY:67 case ACPI_ADR_SPACE_SYSTEM_IO:68 pr_debug("ACPI MEMORY or I/O RESET_REG.\n");69 acpi_reset();70 break;71 }72 73 /*74 * Some platforms do not shut down immediately after writing to the75 * ACPI reset register, and this results in racing with the76 * subsequent reboot mechanism.77 *78 * The 15ms delay has been found to be long enough for the system79 * to reboot on the affected platforms.80 */81 mdelay(15);82}83